net/mlx5e: ethtool, Fix analysis of speed setting

When setting speed to 100G via ethtool (AN is set to off), only 25G*4 is
configured while the user, who has an advanced HW which supports
extended PTYS, expects also 50G*2 to be configured.
With this patch, when extended PTYS mode is available, configure
PTYS via extended fields.

Fixes: 4b95840a

 ("net/mlx5e: Fix matching of speed to PRM link modes")
Signed-off-by: Aya Levin <ayal@mellanox.com>
Reviewed-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>